Tunneling field-effect transistors have a characteristic of being able to operate at a low voltage compared with field-effect transistors currently used as basic elements of semiconductor integrated circuits. Use of tunneling field-effect transistors as basic elements of semiconductor integrated circuits enables reduction of power consumption of the semiconductor integrated circuits. Such a tunneling field-effect transistor is disclosed in, e.g., W. Y. Choi et al., “Tunneling Field-Effect Transistors (TFETs) with Subthreshold Swing (SS) Less Than 60 mV/dec”, IEEE Electron Device Letters Vol. 28, p. 743 (2007).
In existing integrated circuits using field-effect transistors, it is possible to connect a plurality of field-effect transistors in a manner to share the same channel, by disposing gates of the plurality of field-effect transistors in one active region (see, e.g., “Principle of CMOC VLSI design-from systems perspective”, translation supervised by Takashi Tomizawa and Yasuo Matsuyama, Maruzen Co., Ltd.). That is, for connecting, for example, two MOS-type field-effect transistors in a manner to share the same channel, an active region for a source region of one of the field-effect transistors and an active region for a drain region of the other one of the field-effect transistors are provided in common because these active regions are to be adjacent to each other and formed of diffusion layers of the same conductivity type (P type or N type), whereas gates of the respective field-effect transistors are disposed separately from each other. This reduces an area needed and cost, and also suppresses parasitic capacitance and parasitic resistance due to interconnection, leading to boosting of performance.
In the present specification, “active region” refers to a region at which semiconductor is exposed, when a top surface of a wafer is seen in a state that there is nothing formed on the wafer. A device is formed in an active region. There are cases where a plurality of devices are formed in a linked state in an active region.